docs: def _compute_faulting_style_term(self, C, rake):
          """
          Compute and return fifth and sixth terms in equations (2a)
          and (2b), pages 20.
          """
          Fn = float(rake > -135.0 and rake < -45.0)
          Fr = float(rake > 45.0 and rake < 135.0)
  
          return C['a8'] * Fn + C['a9'] * Fr